This invention relates to pouch machines and, more particularly, to an improved rotary knife apparatus used in connection with a pouch form, fill and seal machine capable of handling a wide range of pouch sizes.
The present application is related to the following United States patent applications filed on even date herewith and entitled: "Variable Count Direct Deposit Knife", by P. Dieterlen, Ser. No. 08/338,840, now U.S. Pat. No. 5,515,787; "Low Thermal Inertia Sealer", by M. Wildmoser, Ser. No. 08/338,470, now U.S. Pat. No. 5,502,952; "Convertible Pitch Pouch Machine", by F. Oliverio and B. Makutonin, Ser. No. 08/338,860, now U.S. Pat. No. 5,502,951, and "Tuck Roller with Improved Web Tension Control" by Martin Wildmoser and Frank G. Oliverio, Serial No. 08/338,839, now U.S. Pat. No. 5,611,194 each of which is expressly incorporated herein by reference.
In pouch machines of the known art, such as disclosed in U.S. Pat. No. 3,597,898 which is herewith incorporated herein by reference, a flat web of heat sealable material is continuously fed from upstream of the pouch machine to be longitudinally folded upon itself by a plow or similar device. In this form, the thus-folded web is fed about a sealer which contacts the folded web along vertical heated land areas to form transverse vertical seals and, thus, a series of open pouches along the web. In this way, the web of open pouches is passed around a filler wheel, filled with product and then sealed along the top edge of the web. The web of filled pouches then passes downstream to a motor-driven rotary knife apparatus which cuts the web along the transverse vertical seals into separate individual pouches for subsequent cartoning or other secondary packaging.
It is not unusual for a product manufacturer to run different types of products on a pouch machine. In one situation, the same pre-fill pouch size may be used but one type product might lightly fill the pouch while another type of product might bulge the pouch considerably. In another situation, a different pre-fill pouch size pouch may be required for a different type of product. As these pouches are filled, a chord is defined extending between the vertical seal centerlines on each side of the pouch. In the former case, the chordal distance between the vertical seals will change as a full pouch will define a shorter chord than a lightly filled pouch of the same pre-fill size. In the latter case, the chordal change may be substantial.
In a typical rotary knife apparatus of the known art, a plurality of rigid knife blades extend radially from a major knife hub and another plurality of flexible blades extend radially from a minor knife hub in such a fashion to cooperate in shear with the rigid knife blades. The major and minor knife hubs are supported on respective shafts mounted in a frame. The frame includes a pair of spaced parallel metal plates having bearings attached thereto to support the major and minor knife hub shafts. The shafts include respective driving and driven gears which intermesh so that the rigid and flexible blades come together and shear across the web along the vertical seals to cut off the individual pouches from the web.
In such a rotary knife apparatus, the outer edges of the rigid knife blades extending from the major knife hub lie in a circle. The knife blades are spaced circumferentially about the knife hub such that each knife blade outer edge is equidistant from the other adjacent knife blade edges, this distance usually matching the chordal distance between the vertical seals of the filled pouches so the pouches are cut along the centerlines of the seals. The chordal distance between the rigid knife blade edges must substantially match the chordal distance between the filled pouches to avoid cutting open the filled pouches, that is, cutting beyond the seals.
Adjustments can be made to the radial positions of the rigid knife blades to compensate for slight changes in the chordal distance of the pouches due, for example, to different pouch fills or the like. As the radial position of the rigid knife blade edges is changed from a larger circle to a smaller circle, the chordal distance between adjacent knife blades is changed. This adjustment accommodates smaller chordal distances between the pouches. In a similar fashion, the rigid knife blade edges can be extended radially outwardly to accommodate somewhat larger pouch widths.
Thus, in this regard, before the present invention was made, an advance was provided for facilitating slight radial adjustment of the rigid knife blade edges as disclosed in U.S. Pat. No. 4,872,382 for fine tuning. This was accomplished by the use of a cone having a conical surface and disposed in the center of the cage supporting an inner edge of each knife. The cone is threaded to a screw so that upon rotation of the screw the cone moves axially with respect to the cage. When the cone moves axially, the knife blades, mounted on the conical surface, move radially in and out. Thus, with a simple but precise turning of the screw, a very precise and simultaneous change of the radial locations of all knife blades can be made to fine tune the cutting operation.
A further advance was disclosed in U.S. Pat. No. 5,222,422, which is herewith incorporated herein by reference, wherein the radial position of the rigid knife blade edges is fixed while radially extending and selectively positionable pouch guides are provided to project beyond or retract to the knife blade edges. These guides can be extended or retracted in relation to the knife blades to accommodate changes in pouch chordal distances within a relatively narrow range without having to change the knife blade positions.
While these advances have proven useful, the range of radial adjustment of the knife blades does not accommodate as wide a variation in the pouch sizes or fills as is desired in current pouch form, fill and seal operations. Greater variations of knife blade chordal distances, beyond the limits provided by the known radially adjustable knife blades or pouch guides, typically require the rotary knife apparatus to be returned to the vendor for changing sizes of the major and minor knife hubs. This changeover is typically not feasible in the field due to the complexity in design of the frame support and intermeshing gears. As the major and minor knife hubs are changed, thereby changing their respective diameters, the shaft centers of the major and minor knife hub shafts, and, thus, their respective gears, must be correspondingly changed to accommodate the changeover. Due to this complexity, the changeover can be cost and time prohibitive to a user, thereby resulting in a rotary knife apparatus which is dedicated to a relatively small range of pouch chordal distances.
Accordingly, an objective of this invention has been to provide a rotary knife apparatus which will accommodate a substantially wider range of pouch sizes or variations in pouch fills than can be accommodated by present adjustable knife apparatus having radially adjustable knife blades or pouch guides while at the same time reducing labor and materials costs for the changeover.